Nonwoven fabrics are used in a wide variety of applications. For example, nonwovens of light basis weight and open structure are used in personal care items such as disposable diapers. Nonwovens of heavier weights may be designed with pore structures making them suitable for filtration, or with barrier properties for applications such as housewrap or protective garments for medical or industrial uses.
Various types of nonwovens fabrics have been produced and sold commercially for use as a liquid barrier fabric in building construction or in protective garments. One such commercially available product is manufactured and sold by DuPont under the trademark Tyvek®. This product is formed from flash spun high-density polyethylene fibers which are bonded together to form a nonwoven sheet material.
Other commercially available products have used a nonwoven substrate with a film coating. For example, in Dunaway et al. U.S. Pat. No. 4,898,761, a barrier fabric is disclosed in which a polymer film is laminated to a nonwoven fabric, and the resulting composite sheet material is then needle-punched to provide micropores through the film. The nonwoven fabric is a spunbonded web formed of polyolefin filaments, and the polymer film can be applied to the nonwoven web by hot cast extrusion. U.S. Patent Publication No. 2004/0029469 A1 describes a moisture vapor permeable, water impermeable composite sheet material which is suitable for use as a housewrap material. The composite sheet material includes a nonwoven substrate and an extrusion-coated filler-containing film layer that has been rendered microporous by stretching.
The currently available nonwoven liquid barrier materials have various limitations. Some of the commercially available liquid barrier materials, when used as housewrap, can be easily torn during construction by ladders or by the wind. Liquid barrier materials formed from laminates of a film with a nonwoven substrate require a two-step process which increases the expense. The need exists for an economical barrier material with superior strength as well as excellent water and air barrier properties.